The use of signal-combining, surface acoustic wave (SAW) signal processors in the form of tapped delay lines for encoding and correlating fixed and programmable phase shift key (PSK) codes, for providing dispersive and nondispersive filters for generation and detection of various waveforms, and real time signal correlation and convolution of signals through nonlinear wave interaction, is known in the art. In typical SAW signal processor configurations, a pair of waves may be launched by a respective pair of acoustoelectric transducers (referred to herein as launching ports) at the ends of a common interaction region so as to propagate, along the preferred direction of propagation for the substrate, past a plurality of electrically independent acoustoelectric transducers, called taps, dispersed along the propagation path in an interaction region; in such case the taps comprise a receiving port, or an interaction port; and, the two launched waves proceed serially past each of the taps (in either the same or opposite directions), each tap, however, responding at a given moment in time to different discrete portions (usually called "chips") of the two waves, in parallel. Or, the taps may be used as a launching port so that one wave may be launched in a space-dispersed fashion, discrete portions (chips) thereof (corresponding with the number of taps) being launched simultaneously, in parallel at different propagation delay distances from the other ports; in such case, one of the transducers at an end of the interaction region acts as the receiving or interaction port; and both waves proceed serially to the interaction port, discrete portions (chips) of both waves being received serially in time.
In U.S. Pat. No. 4,016,514 to Reeder and Gilden, DIODE COUPLED TAPPED ACOUSTIC DELAY LINE CORRELATOR AND CONVOLVER, acoustoelectric transducers are disposed at opposite ends of the interaction region which has a plurality of taps dispersed thereon. Each of the taps is connected to a nonlinear product mixer (such as diodes operated in their small signal input range) associated therewith, the combined action of which permits product summation of signal components that provide the correlation or convolution functions (in dependence upon use) of signals applied to the SAW signal processor.
In U.S. Pat. No. 4,024,480 to Reeder and Grudkowski, PROGRAMMABLE, AMPLITUDE AND PHASE, GENERAL TRANSVERSAL FILTER, a SAW signal processor having the additional capability of amplitude and phase programming of the product mixers is disclosed. Therein, the nonlinear product mixers provide video product outputs at the sum and difference of the carrier frequencies of the surface acoustic waves impinging on the related taps, at amplitudes which are selectively adjustable on a tap-by-tap basis to provide a desired transducer tap weighting, and at a selected one of two polarities (or phases displaced by 180.degree.) on a tap-by-tap basis. The weighted, phase selected manifestations from each tap are combined, as by summation, and filtered to form a single complex signal. The SAW processor itself is configured with the known tilted-tap arrangement, to reduce absorption, reflections and spurious signal generation in numerous-tap arrays.
In each of these configurations, there is only one possible relationship between the taps and the waves. In the usual case, where the taps comprise the receiving or interaction port, once the tap configuration is defined so as to establish its relationship with respect to one of the launched waves, its configuration has also been defined and fixed with respect to the other of the launched waves. When the taps are used as a launching port, although the relationship between the wave launched thereby and the wave launched at a single-transducer port at one of the ends of the interaction region can be adjusted by adjusting the spatial relationship of the taps, the relationship between the other launched wave and the single-transducer receiving port is, of course, strictly serial. And, the relationship between the wave launched by the taps and the other wave is fixed by the relationship between the wave launched by the taps and the receiving port. Thus, definition of one relationship inherently carries with it an automatic definition of the other relationship. This may be referred to as a unidimensional wave/tap dependence which renders it impossible to provide independent relationships between the two waves and the receiving or interaction port, regardless of how the SAW module is driven. One consequence of this interdependency of tap relationships to the respective waves is illustrated in the aforementioned Reeder and Gilden patent wherein the achievement of complex processing, such as performance of the discrete Fourier transform, requires utilization of the SAW processor module (including the product mixers relating to its taps) in conjunction with numerous external circuit elements in a complicated, time-related system. And, although utilizing the programmable product mixers of the Reeder and Grudkowski patent with a SAW module configured as in the Reeder and Gilden patent solves the functional problem in the theoretical sense, it does not alleviate the problem due to the fixed relationship between the taps and the other two ports which inherently provides excessive absorption and reflection in a device having sufficient taps (e.g., 256 or more) to segment the waves for meaningful analysis.